Low profile antennas for communication on the move (COTM) are used in numerous commercial and military applications, such as automobiles, trains and airplanes. Mobile terminals typically require the use of automatic tracking antennas that are able to steer the beam in azimuth, elevation and polarization to follow the satellite position while the vehicle is in motion. Moreover, the antenna should be “low-profile”, small and lightweight, thereby fulfilling the stringent aerodynamic and mass constraints encountered in the typical mounting of antennas in airborne and automotive environments. The invention addresses this and other needs.
The capability to steer the polarization of the beam is necessary when the antenna receives a linear polarized signal and the antenna platform is mobile. Previously, the accuracy of polarization tracking in digitally controlled phased arrays was solely determined by the accuracy of the polarization phase shifters, determined by the number of bits in the phase shifter. Other approaches to steering the polarization have been directed towards controlling the quantization lobes in an attempt to manage the quantization of the polarization steering control. However, quantization lobes are just a secondary effect of the quantization. Moreover, this approach does not overcome the fundamental limitation imposed by the polarization phase shifters on the accuracy of polarization tracking. Thus, a need exists for an approach to improve polarization tracking control using a predetermined number of bits in a polarization phase shifter.